currently using opiates or who ever met criteria for opiate dependence and those taking medications for any current psychiatric (including prescribed or unprescribed anxiolytics) or medical condition were excluded. Women were excluded from the study if they were using hormonal contraceptives or were either perimenopausal or postmenopausal. All subjects underwent a complete medical evaluation, including electrocardiography and laboratory tests of renal, hepatic, pancreatic, hematopoietic, and thyroid functions, to ensure good physical health. All study procedures were approved by the Human Investigation Committee of the Yale University School of Medicine and all participants signed a written informed consent.
